Digital subscriber line access multiplexer writing validation

ABSTRACT

A test system detects proper connection wiring in a connection frame between a customer&#39;s lines and a DSL Access Multiplexer (DSLAM). A multi-loop tester at a central office generates a test signal on low frequency lines to a customer&#39;s connection in a connection frame. A signature circuit is electrically connected between the customer&#39;s connection in the connection frame for the low frequency lines and the DSLAM. The signature circuit responds to the test signal and generates a signature signal. The multi-loop tester senses the signature signal to verify that the DSLAM is properly connected to the customer&#39;s lines.

FIELD OF THE INVENTION

This invention relates to a DSLAM (Digital Subscriber Line AccessMultiplexer) writing validation methods and systems. More particularly,the invention relates to validating proper network connections between aDSLAM and the lines to a customer location.

BACKGROUND INFORMATION

When DSL service is added to the service for a telephone customer, aDSLAM (Digital Subscriber Line Access Multiplexer) must be added to theequipment and connected to the customer's telephone lines through across-box or other connection frame. The cross-box or connection framemay have many connections to many customers. A difficulty arises in thatthe technician making the connections in the cross-box may not properlyconnect the DSLAM to the customer's telephone lines. For example, theconnection from the DSLAM may be made to another customer's lines ratherthan the telephone lines of the intended customer. When this occurs, theDSL modem at the customer's location will not synchronize with a DSLAMand the customer's DSL service will not activate.

From the perspective of the telephone company technician, the failure ofthe DSL service to activate could be an improper connection at thecustomer's location, or it could be an improper connection at thecross-box or connection frame connecting the DSLAM to the telephonelines for the customer. Accordingly, the telephone company does not knowwhether to dispatch a service person or technician to the customer'slocation or to dispatch a different service person to the telephonecompany equipment location containing the cross-box or connection frameconnecting the DSLAM to the customer's telephone lines.

SUMMARY OF THE INVENTION

In accordance with this invention, this problem and other problems havebeen addressed by placing a signature circuit on a low frequency side ofa Digital Subscriber Line Access Multiplexer connection to thecustomer's lines. Using multiple loop testing techniques, the servicetechnician can, from a central location, test the customer's connectionto the DSLAM.

In one embodiment of the invention, a test system is provided to detectproper connection wiring in a connection frame between the customer'slines and the DSLAM. A multi-loop tester at a central office generates atest signal on low frequency lines to a customer's connection in aconnection frame. A signature circuit is electrically connected betweenthe customer's connection in the connection frame for the low frequencylines and the DSLAM. The signature circuit responds to the test signaland generates a signature signal. The multi-loop tester senses thesignature signal to verify that there is proper connection wiringbetween the customer's lines and the DSLAM.

In another embodiment of the invention, a method is performed fortesting for proper connection wiring in a connection frame between thecustomer's lines and the DSLAM. In the method, a test signal isgenerated over the low frequency lines from a central office through aconnection for a customer in the connection frame to a signature circuitbetween the connection frame and the DSLAM. A signature signal isgenerated at the signature circuit in response to the test signal. Thesignature signal is detected on the low frequency lines to verify thatthe DSLAM is connected to the lines of the correct customer.

These and various other features as well as advantages, whichcharacterize the present invention, will be apparent from a reading ofthe following detailed description and a review of the associateddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a preferred embodiment of the invention with a signaturecircuit 126 located on the low frequency connection line between thecrossbox and the DSLAM.

FIG. 2 shows one embodiment of a signature circuit.

FIG. 3 illustrates a test signal generated during multi-loop testing todetermine whether the DSLAM is properly connected to the customer'slines.

FIG. 4 shows another preferred embodiment where the signature circuit islocated in a connecting shoe 414 for cable connectors between a DSLAMand a connection frame.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIG. 1, a customer's telephone 102 is connected via twisted pairlines 104 to a cross-box 106. Typically, when the customer is beingprovided only Plain Old Telephone Service (“POTS”), then a connection inthe cross-box 106, or connection frame, connects the twisted pair lines104 through connection wires 108 to low frequency lines 110 connected toClass 5 switches 112 at a central office. The Class 5 switches interpretthe dialed telephone number and work with the Public Switched TelephoneNetwork (“PSTN”) 114 to connect the customer's call to its destination.

When the customer has a personal computer 116 or otherwise wishes to addDigital Subscriber Line (“DSL”) service, a DSL Access Multiplexer(DSLAM) 118 is added to the circuit for the customer. Typically, the DSLservice is used by the subscriber to connect to an Internet ProtocolNetwork 119. To add the DSLAM 118, a low frequency side of the DSLAM 118is connected to low frequency lines 110 to the Class 5 switches 112.This connection is done by breaking or disconnecting connection lines108 in the cross-box 106 and reconnecting a low frequency connectionwith connection lines 120 to lines 111. At the same time, a connectionpassing all frequencies from the DSLAM 118 and the customer is made byadding connection lines 122 to lines 124. Lines 104, 110, 111 and 124are usually twisted pair lines. Now there is a twisted pair connectionfrom the customer's lines 104 through the connection lines 122 andthrough lines 124 to DSLAM 118. If the connection lines 120 and 122 arenot properly installed, then the DSL service to the customer will notoperate.

To test the proper connection of the DSLAM 118 in the cross-box to thecustomer's lines, a multi-loop tester 113 at the central office providesa test signal over the low frequency lines 110, 111 and connecting lines120 to a signature circuit 126. The signature circuit 126 will generatea signature signal in response to this test signal, and this signaturesignal may be detected by the multi-loop tester 113 of the centraloffice through the low frequency lines 110, 111 and connecting lines120, and Class 5 switches 112. One embodiment for the signature circuit126 will be described hereinafter with references to FIGS. 2 and 3.

The signature circuit 126 might be most easily applied to the network byincorporating it into a protector circuit 128. The protector circuit 128is used to protect the DSLAM 118 from voltage or current surges due tolightening strikes on the network. These protector circuits 128 areregularly serviced and replaced. Accordingly, incorporating thesignature circuit 126 into the protector circuit 128 provides an easymethod for installing the signature circuit 126. A test signal to testlow frequency lines 110 and 111 and their proper connection through line120 in the cross-box 106 is supplied from the multi-loop tester 113through the Class 5 switches 112.

FIG. 2 shows one preferred embodiment for the signature circuit. Thevoltage polarity of the test signal is indicated in FIG. 2 between line111A and line 111B (i.e. wires of twisted pair line 111 of FIG. 1).Diode 206 allows current to flow only from node 201 to node 203.However, an avalanche break-down diode, or zener diode, 208 will notpermit a current flow I1 until the voltage across zener diode 208exceeds its breakdown voltage VZ. When this occurs, the voltage betweennodes 210 and 203 will be very close to the break-down voltage for zenerdiode 208 as the forward bias voltage across diode 206 will be verysmall.

Above the breakdown voltage VZ of zener diode 208, current I1 will flowthrough resistor 212, zener diode 208, and diode 206 and the magnitudeof such current will be substantially equal to (V1−VZ)/R the resistanceof resistor 212. Thus, by applying a voltage pulse greater than VZbetween lines 202 and 204 and observing the current through the linesduring the pulse, a proper connection at the DSLAM 118 can be testedremotely from the central office.

In FIG. 3, the voltage pulse V1 is the test signal, and the resultantcurrent signal I1 is the signature signal. When a test signal V1(voltage pulse for example) is applied on twisted pair wires 111A and111 b and the magnitude of the pulse exceeds the breakdown voltage ofzener diode 208, current will flow through the signature circuit 126,and this current can be sensed as the signature signal. If the signaturecircuit 126 does not detect the test signal and generate the signaturesignal, then it is likely that the connection line 120 (FIG. 1) in thecross box has been improperly installed.

Of course other signature circuits might be designed to provide avoltage response, a frequency response, or a phase response. If the testsignal were a frequency signal, the signature circuit would be designedto detect the test frequency signal and generate and return a signaturefrequency to the tester at the central office. The signature frequencywould differ from the test frequency. If the test signal were a phasesignal, the test signal would be transmitted as frequency pulses at apredetermined phase, The signature circuit would detect the frequencypulses, and send back to the central office frequency pulses with thephase shifted relative to the test signal pulses.

In FIG. 4, a DSLAM 402 is connected to a cross-connection frame 400through a cable 404 carrying multiple paired wires for multiple lines.Each wire pair pin connection in the cable 404 will have a pair of pinsin the connector 410. FIG. 4 illustrates an embodiment of the testingsystem and method where a signature circuit is embodied in a shoe 414plugged between connectors 410 and 412. In the shoe there are multiplesignature circuits—one signature circuit between each telephone-line,wire-pair connection in the shoe. Each signature circuit in test shoe414 can be installed to connect between each pair of pins.

Between one of connectors 406 and 408 or connectors 410 and 412, asignature circuit test shoe 414 is inserted. In FIG. 4, the test shoe414 has pins that plug into sockets of connector 410. The test shoe 414has sockets to receive pins (not shown) of connector 412. Thus, testshoe 414 is connected between connector 410 and connector 412.

Connector 412 connects to the connection frame 416 where wiring patchesare made to connect the DSLAM 412 to the customer's lines. Without DSLservice, the customer lines would be connected by patch lines 418. WithDSL service, the patch lines 418 are disconnected and low frequencypatch lines 420 are connected between a DSLAM connection array 421 and apublic switching telephone connection array 422. Patch lines 424 areconnected between the DSLAM connection array 421 and a customerconnection array 425.

A particular signature circuit has been shown and described, but it willbe appreciated by one skilled in the art that any number of voltagesignal, current signal, frequency signal, signature devices could beinserted as a signature circuit to implement the present invention.

While the invention has been particularly shown and described withreferenced to preferred embodiments thereof, it will be understood bythose skilled in the art that various other changes in the form anddetails may be made therein without departing from the spirit and scopeof the invention.

1. A test system for detecting a proper connection between a customer'slines and a DSL Access Multiplexer, comprising: a multi-loop tester at aremote location for generating a test signal on the customer's lines; asignature circuit electrically connected between the customer's linesand the DSL Access Multiplexer; wherein the signature circuit inresponse to the test signal generates a signature signal; and whereinthe multi-loop tester senses the signature signal to verify that theproper connection exists between the customer's lines and the DSL AccessMultiplexer.
 2. The test system of claim 1 wherein the signature circuitis incorporated into a lightening protection circuit.
 3. The test systemof claim 1 wherein the signature circuit is incorporated into aconnection shoe between cable connectors.
 4. A method for testing for aproper connection between customer's lines and a DSL Access Multiplexer,the comprising: generating a test signal over the customer's lines froma remote location; generating a signature signal at a location betweenthe DSL Access Multiplexer and the customer's lines in response to thetest signal; and detecting the signature signal at the remote locationto verify the proper connection between the DSL Access Multiplexer andthe customer's lines.
 5. The method of claim 4 wherein the signaturecircuit has a zener diode and at least a portion of the test signalexceeds the avalanche break-down voltage of the zener diode.
 6. Themethod of claim 5 wherein the signature signal is generated when theavalanche break-down voltage of the zener diode is exceeded.